It is often desired to withdraw water from a pond or other accumulation of water. This is accomplished in a variety of ways. For example, U.S. Pat. No. 3,927,534 (Larson) shows an intake which is fixed to the bottom of a body of water and thus supplies water from a location fixed with respect to the bottom of the body. U.S. Pat. No. 4,405,458 (McHugh, Jr.) shows a weir which floats on the surface of the body and, thus, supplies water from the top of the body. Other supply devices are known which supply water from fixed locations but which may have float controlled valves to stop the flow of water when the level of the body is too high or too low.
One problem faced by water and soil conservation engineers is that the water in a pond varies as a function of the depth of the water. At increased depths, for example, the oxygen content of the water may be too low, while at shallow depths, the algae or other plant life growth may be significant enough that the water is not useful. Accordingly, it is often desirable to supply water from a selected depth.